High-intensity discharge lamps (HID lamps) are a type of electric light that produces bright illumination by passing an electric current through a gas. These lamps contain a small amount of gas, such as mercury or sodium, which emits light when energized. HID lamps are commonly used in outdoor lighting, such as streetlights and stadiums, due to their high efficiency and long lifespan. HID lamps come in various types, including metal halide, high-pressure sodium, and low-pressure sodium lamps. They are known for their ability to produce a significant amount of light with relatively low energy consumption. However, they typically require a warm-up period to reach full brightness and may need a ballast to regulate the electrical current.